The present invention relates to a video camera having a .gamma.-correction circuit for correcting level characteristics of a luminance signal included in a video signal.
A picture tube of a television receiver has input/output characteristics of non-linearity called a gamma. Therefore, the video camera is designed in such a way that a .gamma.-correction circuit having reverse characteristics with respect to the picture tube is provided and the .gamma.-correction of a video signal is performed by the .gamma.-correction circuit to send the resultant signal to the television receiver thereby to cancel the .gamma.-characteristics of the picture tube. As a result, a pictorial image equal to an input image of an image pick-up device of the video camera is displayed on the television receiver.
As a .gamma.-correction circuit, hitherto, there are proposed those of various types.
For example, in JP-A-58-130676, there is disclosed a .gamma.-correction circuit which is designed in such a way that a video signal which was subjected to .gamma.-correction and a video signal which was not subjected to the .gamma.-correction are added to each other and there sultant addition ratio is made to be variable thereby to obtain a video signal which was subjected to the .gamma.-correction with a desired gamma value.
Moreover, in JP-A-55-140372, there is disclosed a technique which is arranged in such a way that two luminance signals which were subjected to the .gamma.-correction with different gamma values are mixed with each other and the resultant mixture ratio is changed in accordance with a signal distribution state of the luminance signals.
Further, in JP-A-1-206775, there is disclosed a technique which is arranged in such a way that a low-frequency component of a luminance signal is subjected to .gamma.-correction with a fixed gamma value, a high-frequency component thereof subjected to the .gamma.-correction with a gamma value which is changed in accordance with the level of the luminance signal, and the low-frequency and high-frequency components which were subjected to the .gamma.-correction are added to each other thereby to prevent the degradation of an S/N ratio so as not to amplify the noise contained in the high-frequency component of the luminance signal whose level is low.